Method

Make the speck toffee: cook the bacon in a large sauté pan over medium-high heat until crisp, about 5 minutes on each side. Strain the rendered fat through a paper towel and save the bacon for another use. Measure out 5 tablespoons of the fat and add to a medium saucepan. Add the butter and melt over medium heat while stirring with a wooden spoon. Add the sugar and raise the temperature to medium-high. Remove from the heat and stir vigorously until smooth. Add a pinch of salt and stir to combine. Pour the toffee onto a parchment paper–lined baking tray and spread it out as thinly as possible. Let cool to room temperature, about 20 minutes. Freeze until very stiff.

Break the toffee into small pieces and place in a food processor. Pulse until the toffee has the consistency of gravel. Measure out 1 cup and set aside.

Preheat the oven to 375ºF. Generously butter 10 cups in a 12-cup muffin tin and dust with flour. Set aside.

Combine 1/2 cup of the toffee and 3 tablespoons of the maple syrup in a small saucepan. Stir over low heat until the toffee has melted. Spoon a scant tablespoon of the maple toffee into each cup of the prepared muffin tin. The toffee layer should be about a quarter of an inch thick.

Cream the butter with the brown sugar and maple sugar in a stand mixer fitted with a paddle attachment. Add the remaining maple syrup and combine on low speed. Add the egg yolks and mix until smooth and fluffy, about 3 minutes. Scrape down the sides of the bowl and mix for another minute.

Sift the flour and baking soda on top of the butter mixture. Using a rubber spatula, fold in the dry ingredients until just combined. Add the remaining toffee pieces and fold to combine. Transfer the batter to a large bowl and set aside.

Clean the stand mixer bowl, reattach it to the stand mixer, and fit the mixer with a whisk attachment. Add the egg whites and begin whipping them. When the egg whites are foamy, add the granulated sugar in a steady stream with the mixer running. Once all of the sugar has been added, increase the mixer speed to the highest setting and whip until the mixture forms soft peaks. Add the meringue to the reserved batter in thirds, folding in each addition with a rubber spatula.

Scoop a scant 1/4 cup of batter into each prepared cup of the muffin tin. Bake the cakes for 5 minutes, then rotate the pan 180 degrees and bake for an additional 5 minutes or until golden.